Subject to any ageements with holders of particular bonds, all moneys available for carrying out the purposes of this part and declared by the agency to be surplus moneys which are not required to service or retire bonds issued on behalf of the agency, pay administrative expenses of the agency, accumulate necessary operating or loss reserves, or repay loans to the agency from the General Fund shall be used by the agency, with respect to existing housing developments, to provide special interest reduction programs, financial assistance for housing developments or subsidies for occupants or owners thereof, or counseling programs, as authorized by this division.